“Cumulative broadcasting service” and “Server-type broadcasting service” sometimes refer to a service that data distributed via broadcasting are automatically accumulated temporarily within a receiving apparatus and updated and a user watches the cumulative data at desired time.
Conventional techniques will now be described with reference to drawings. The same elements and portions will be denoted at the same reference symbols among a plurality of drawings and will not be described redundantly.
FIG. 8 is an explanatory diagram of a phase of accumulating data for a cumulative broadcasting service in a receiving apparatus according to a conventional technique.
Before describing the phase of accumulating data, a structure of the conventional receiving apparatus will be described first.
The conventional receiving apparatus comprises a tuner 210, a TS decoder 220, accumulating means 230, an AV decoder 240, graphics drawing means 250, presenting means 260, inputting means 270, a CPU 281, a RAM 282 and a ROM 283.
The tuner 210 receives a broadcasting wave and outputs an MPEG (Moving Picture Experts Group) 2-TS (Transport Stream) which is the signal format of a bit stream in which video, speech and data are multiplexed with each other. MPEG2-TS is defined in ISO/IEC 13818-1 which is an international standard, “Information Technology-Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to about 1.5 Mbit/s—Part 1: Systems.” and used as a standard in the world for multiplexed transmission of video, speech and data in digital broadcasting.
The TS decoder 220 receives an MPEG2-TS outputted from the tuner 210, and separates video, speech and the other data from each other and outputs or deciphers a code.
The TS decoder 220 comprises a descrambler 221, a PID filter 222 and a section filter 223.
The descrambler 221 deciphers codes on an MPEG2-TS used in digital broadcasting. As such codes, Multi-2 or the like is used in Japan. The PID filter 222 extracts particular information, such as particular video alone, from an MPEG2-TS supplied to the TS decoder 220. Information is multiplexed in the unit of packets which are called TS packets defined by MPEG2-TS and each having 188 bytes, and distinguished by a 13-bit field which is added to each packet and called PID (packet id). For example, when video alone needs to be extracted from an MPEG2-TS in which video, speech and data are multiplexed with each other, it is only necessary to selectively extract those TS packets which have PIDs which are assigned to video. The PID filter 222 is capable of extracting TS packets which have one PID or a plurality of PIDs designated in advance from a received MPEG2-TS.
Further, the PID filter 222 supplies three outputs, (1) one to the accumulating means 230, (2) another to the section filter 223 and (3) the other to the AV decoder 240, and is capable of designating one or more than one PIDs to each output and simultaneously processing them.
The section filter 223 selects a data structure called a DSM-CC section (hereinafter sometimes referred to simply as “section”) contained in an MPEG2-TS outputted from the PID filter 222.
DSM-CC and a DSM-CC section are a data structure of maximum about 4 K bytes defined in ISO/IEC 13818-6 which is an international standard, “Part 6: Extensions for Digital Storage Media Command and Control,” contains fields such as table_id which is 8 bits, table_id—extension of 16 bits, section_number of 8 bits and version_number of 5 bits which expresses a version, and identified by means of these fields. Hence, in the same transmission path, the contents of sections in which these fields are identical are the same with each other (during a period in which these ids are used up but will not be assigned once again).
On some occasions, in the field of data broadcasting, data content refers to still pictures which constitute a data broadcast or such data described in BML (Broadcasting Markup Language), which is a descriptive language for descriptions on the screen, created on the premise that the data will be presented to users.
Further, in cumulative broadcasting, for the purpose of managing data content, video, speech and the like stored in a cumulative medium of a receiving apparatus, an additional information file called meta data is used. Meta data herein referred to are described by XML (eXtensible Markup Language), etc. Stored in meta data are information needed to manage the version of data content, expiration dates and the like. With the meta data interpreted, it is possible to update the data content, video, speech and the like stored by the receiving apparatus in the cumulative medium or delete those which have already expired.
While data content and meta data are information in the so-called file format, as an air format for transmission of such information, a scheme called a DSM-CC data carrousel is used. A DSM-CC data carrousel is transmitted using the sections described earlier. In other words, this is an air format located in an upper layer above the sections. Files are transmitted in the unit of so-called modules.
Like DSM-CC sections, modules and DSM-CC data carrousels are defined in ISO/IEC 13818-6, an international standard.
The accumulating means 230 is a hard disk drive. The accumulating means 230 is capable of receiving and accumulating streams, such as an MPEG2-TS, outputted from the TS decoder 220, outputting an accumulated MPEG2-TS, or writing and reading data developed in the RAM 282 as a file.
The accumulating means 230 includes an area 231 in which streams are accumulated and an area 232 in which files are accumulated. These areas correspond to partitions which are physically ensured on the accumulating means 230.
With respect to the area 231 in which streams are accumulated, the byte count of a block, which is the minimum unit for writing in the accumulating means 230, is set relatively large, so as to realize continuous writing/reading at a high speed.
On the other hand, with respect to the area 232 in which files are accumulated, the byte count of a block is relatively small, for the purpose of enhancing the processing speed for reading and writing of a small file through random accesses and improving the utilization efficiency of the area, instead of prioritizing continuous writing.
The AV decoder 240 receives an MPEG2-TS outputted from the TS decoder 220, decodes a multiplexed video and speech stream from the MPEG2-TS and accordingly converts into a video signal and a speech signal.
The graphics drawing means 250, under the control of the CPU 281, displays GUI (Graphic User Interface) on the screen and pastes in the GUI screen the video signal outputted by the AV decoder 240.
The presenting means 260 is a telereceiver or a CRT (Cathode Ray Tube) which comprises a video input and a speech input. The presenting means 260 may comprise a speaker.
The inputting means 270 is an input device which accepts manipulations given by a viewer, and comprises an infrared remote controller and a light receiver unit for the infrared remote controller for instance.
The CPU 281 is a central processing unit used in an ordinary computer (CPU; Central Processing Unit).
The RAM 282 is a main memory RAM (Random Access Memory) formed by a semiconductor memory and used in an ordinary computer.
The ROM 283 is a ROM (Read Only Memory) for storing a program and the like formed by a semiconductor memory and used in an ordinary computer.
The phase of accumulating data for a cumulative broadcasting service in the conventional receiving apparatus will now be described.
First, the PID filter 222 is provided with designation as for the PID of video and speech to be accumulated. In response, as denoted at the arrow 811 in FIG. 8, an AV stream is outputted. On some occasions, a partial TS refers to such an MPEG2-TS which is obtained by extracting only one pair of video and speech in particular from the MPEG2-TS containing various data and added some additional information. The AV stream denoted at the arrow 811 can also be said as a partial TS.
Next, the AV stream 811 is stored in the area 231 of the accumulating means 230 for accumulating streams, whereby AV streams get accumulated in the accumulating means 230 as streams of data 801.
Meanwhile, in the PID filter 222, PIDs are designated with which data of a data carrousel, which contains such data as MBL documents or still pictures to be accumulated, are transmitted. As a result, the MPEG2-TS of a data carrousel designated at the arrow 821 is extracted.
Next, a desired section is selected from the MPEG2-TS of the data carrousel by the section filter 223 and outputted as data in the section format. Thus outputted section format data are stored by the CPU 281 in the RAM 282, as a data carrousel is decoded, a file transmitted by means of the data carrousel is created.
Then, the created files are stored in the area 232 for accumulating files of the accumulating means 230 as file 802.
If there are meta data within thus created file, the CPU 281 interprets the meta data. Meta data contain information for controlling accumulated content, such as correlation between files to be accumulated, information regarding names and the like for presentation to users, information regarding expiration dates, copyright and the like, and information regarding versions, scheduling and the like of updating.
FIG. 9 is an explanatory diagram showing a phase of reproducing data for a cumulative broadcasting service in the conventional receiving apparatus.
First, as denoted at the arrow 911, data 802 stored in the file accumulation area 232 of the accumulating means 230 are read out (802 is a BML document for instance).
Next, storing in the RAM 282 is carried out, the CPU 281 starts up a BML engine and the BML document is interpreted, whereby the graphics drawing means 250 creates a GUI screen.
The status of the BML engine then transits in accordance with an input provided through the inputting means 270.
Assume now that reproduction of video and speech is instructed during the status transition. As denoted at the arrow 921, the AV streams 801 stored in the stream accumulation area 231 of the accumulating means 230 are outputted and fed to the PID filter 222.
Following this, as denoted at the arrow 922, these are supplied to the AV decoder 240 via the PID filter 222 and reproduced.
By the way, a possible state in cumulative broadcasting may be that video and speech used for cumulative broadcasting, data content and meta data are transmitted from the broadcast. On this occasion, it is necessary for the accumulating means to receive and accumulate the video and speech and the data content simultaneously. Further, concurrently with the accumulation, the accumulated content is processed by receiving, decoding and interpreting the meta data.
While a high-volume cumulative medium which can be accessed at random, such as a hard disk and a DVD (Digital Versatile Disk)-RAM, may be selected as the cumulative medium, such a random access accompanies physical movements of a head for reading and writing. Hence, writing of data in the cumulative medium or retrieval of data from the cumulative medium is interrupted for or over a certain period of time before and after the head movements, and when reading and writing accompanying head movements are demanded even for a small file during continuous reading and writing of video and speech which need a particularly high transfer rate, reading and writing of the video and speech may not complete in time.
A hard disk in particular for example, being tuned so as to suit reading and writing of a relatively small file through random accesses, is not good at reading and writing at a high transfer rate.
A conventional approach therefore is to prepare a file mode which is optimized for reading and writing of a file and a stream mode which is optimized for reading and writing of a stream such as video and speech, and to use a block having a larger byte count in which the cumulative medium is physically read out or written in the stream mode thereby enhancing capabilities (Methods for this include a method which realizes this by means of an operation mode of the cumulative medium itself and a method which logically realizes this by means of software which is executed by a CPU of the receiving apparatus.).
However, an area which is written in under the stream mode and an area which is written in under the file mode are associated with partitions which are physically different areas on the cumulative medium. Because of this, the head must move a far distance between the stream mode and the file mode, and occurrence of processing in the file mode in the middle of the stream mode serves as an obstacle hindering the processing under the stream mode (Although it is possible to avoid a drop in processing speed with better capabilities of the cumulative medium such as a hard disk, the CPU of the receiving apparatus and the like of course, this may make the apparatus expensive or increase the consumption power.).